Metrics and Diagnosis

Metric/MethodCategoryCalculation/Core PrincipleSimulation Usage/Diagnostic Value
HistogramBasic StatsPixel value binning, 1D distributionOverall exposure distribution, dynamic range check
Quantiles (p50/p90/p99)Basic StatsPercentiles of CDFLocating median color casts (e.g., rg_mid p50)
Mean/MedianBasic StatsWeighted average or p50Overall exposure level baseline
Standard DeviationBasic StatsSqrt of varianceContrast quantification (film usually lower than digital)
SkewnessBasic Stats3rd central momentAsymmetry, negative skew = more highlight detail (film trait)
KurtosisBasic Stats4th central momentTail thickness, high kurtosis = clipped blacks/whites
EntropyBasic Stats-Σp(x)log p(x)Information density, grain increases local entropy
Clipped Pixel RatioBasic StatsRatio of extreme valuesProportion of dead blacks and blown highlights
Dynamic RangeBasic Statsp99/p1 or p995/p005Effective latitude quantification
RgMid/BgMidColor ScienceR/G, B/G ratio at mid-grayWhite balance baseline, deviation from 1.0 = cast
Lab Space StatsColor ScienceLab* channel mean/varL* lightness latitude, a*/b* shows cast direction
CCT & TintColor ScienceInverted gray point estimationWhite balance calibration verification
Saturation DistColor ScienceHSV S-channel skewnessAsymmetric saturation distribution of film
Delta E 2000Color ScienceCIEDE2000 formulaDifference between simulation and target scan
PSD (Power Spectral Density)Frequency/TextureRadial avg of FFTGrain frequency distribution (1/f^β noise)
MTFFrequency/TextureContrast vs Spatial FrequencySharpness quantification, edge retention
Laplacian VarianceFrequency/Texture2nd derivative statsFast sharpness estimation
LBP (Local Binary Patterns)Frequency/TextureLocal texture codingGrain structure difference quantification
SSIM/MS-SSIMPerceptual/StructStructural SimilarityStructure fidelity (Sim vs Ref)
LPIPSPerceptual/StructVGG feature distancePerceptual distance, better than L2
CID (Contrast Index)Perceptual/StructCIE-based contrast indexContrast difference quantification
Dye Density CurveFilm SpecificDensity vs log ExposureH&D curve fitting (R²/RMSE)
Mask DensityFilm SpecificOrange mask a*/b* offsetNegative-to-positive mask correction verification
Reciprocity CurveFilm SpecificTime-Density non-linearityShort/Long exposure simulation accuracy
Grain AutocorrelationFilm SpecificSpatial correlation of noiseFilm grain is not pure random noise
HSV HistogramColor Space1D/Multi-D binningHue shifts, saturation asymmetry
Lab HistogramColor SpaceLab* channel statsLightness latitude, color cast direction
YCbCr HistogramColor SpaceLuma/Chroma separationChroma range check (film gamut is often narrower)
RGB Joint Hist (3D)Color SpaceR×G×B cube binningColor mapping linearity, neutral axis shift
2D Joint HistSpatial RelationJoint prob (e.g., R-G)Channel correlation, neutral axis diagonal check
GLCMSpatial RelationCo-occurrence probabilityGrain texture quantification, uniformity
Tile HistogramSpatial RelationBlock-wise statsVignetting, uneven development detection
Power Spectrum HistFrequency2D FFT radial binningEnergy vs Frequency, grain feature extraction
Wavelet HistFrequencyMulti-scale coeff statsMulti-layer grain structure capture
Gradient HistGradient/EdgeEdge direction statsSilver halide crystal anisotropy detection
Laplacian HistGradient/Edge2nd derivative statsSharpness/Softness measurement
Ratio Hist (R/G)Ratio/Log SpaceChannel ratio binningIllumination-robust cast detection
Log Exposure HistRatio/Log SpaceLog-space binningDirect fitting of H&D curve toe/shoulder